Electrode system of unsymmetrical conductivity



ELECTRODE SYSTEM OF UNSYMMETRICAL CONDUCTIVITY Filed March 4, 1956 ATTORNEY Patented Sept.`26, 1939 UNITED STATES PATENT CFFICE Gilles Holst and Willem Christiaan van Geel, Eindhoven, Netherlands, assignors to N. V.

Philips Gloellampeni'abrlcken,

Netherlands Eindhoven,

Application March 4, 1936. Serial No. 67,052 In Germany March 9, 1935 3Claims.

The invention relates to an electrode system of unsymmetrical conductivity formed by t'wo layers of different emitting capacity which are separated from one another by a layer of insulating material.

It is known already that if cuprous oxide rectiers form the starting point, a three-electrode system may be produced by providing in the semi-conductive oxide layer a grid to' which an auxiliary voltage is applied in order to act upon the electron current owing from the copper electrode to the semi-conductor. Experiments have shown, however, that a detector thus produced does not function satisfactorily.

Furthermore, it has previously been proposed to form a detector as a dry rectifier in which the electron current between the metallic electrode and the semi-conductor is acted upon by the field variation of a magnetic circuit of which the rectifier i'orms a part. This form of construction has the drawback that it takes up much room and cannot be operated in a simple manner.

The invention has for its object to provide a detector or ampliiier capable of taking the place of the present valves with thermal emission which are complicated and expensive in initialcost as well as in operation, for example, due to the current consumption for heating the cathode.

According to the invention, an electrode system of unsymmetrical conductivity is formed by two layers of different emitting capacity which are separated from one another by a layer of insulating material, and embedded in the insulating intermediate layer is a grid provided with a supply conductor for applying potentials for the control of the electron current and/or for screening purposes.

A detector of this kind may consequently take the place of a usual detector or three-electrodeamplifying valve for it likewise comprises both an emitting electrode and an electrode which does not or substantially does not emit and, between these two electrodes, a grid which corresponds to a grid arranged in a valve in the vacuum between the cathode and the anode. In accordance with the inventionz the grid is located in the insulating layer, which. as has been found, has the most favorable result. It is clear that the number of grids need not be limited to one.

A favorable form of execution of an electrode system according to the invention is that which follows:

The grids are constituted by perforated layers oi' conductive material which are contained in the insulating intermediate layer, said perforated layers being obtained, for example. by applying to one of the electrodes alternately an insulating layer and a perforated conductive layer and finally to the last conductive layer again an insulating layer. It is consequently possible to form electrode systems which correspond to the present radio valves having three or more electrodes such as, for example, the triodes, tetrodes, pentodes, hexodes, etc.

It is particularly important and advantageous that the insulating intermediate layer which contains the grids be formed independently of the adjacent electrode layers, for this renders it possible to control at will both the thickness of the layer and the position of the grids. The intermediate layer may be constituted of, `for example. artificial resin which is applied in liquid condition to one of the electrodes. It is thus possible to apply a perfectly homogeneous layer.

It is of course very desirable to make the intermediate layer as thin as possible in order to raise as much as possible the electrical eld strength between the main electrodes, as this has a great effect on the favorable operation. Due

to the presence of a conductive grid there arises however the possibility that due to the too slight thickness of the insulating layer at a single, for example, accidentally projecting point, said grid may short-circuit one of the electrodes. In one favorable form of execution the risk of a short circuit is avoided by providing the grids with an insulating coating before they are applied to the insulating layer.

When choosing a grid material it should be considered that on account of its own emission a grid of emitting material acts upon the electron current between the anode and the cathode.

According to a favorable mode of execution use is therefore made of a grid material being a semior bad conductor and having a slight emitting capacity.

The invention will be explained more fully with reference to the accompanying drawing which represents, by way of example, one embodiment thereof.

The main electrodes I and 2 are formed, respectively, by a conductor consisting of a metal of high emitting capacity such as aluminum, copper or silver and by a semi-conductor as is usual in dry rectiflers. Selenium is a very suitable material for the semi-conductor.

The drawing represents, by way of example, a six-electrode-system. Besides the main electrodes I and 2 there are consequently four further electrodes (screen and control grids and the Y like). The main electrodes are separated from one another by means of an insulating material 3. In the example shown there are a plurality of grids which have been applied so as to alternate with the insulating layers.

In producing such an electrode system one starts, for example, with a main electrode 2 with smooth contact surface. To this electrode is applied, for example, by spraying, an insulating layer 3 to which is applied a grid l which is provided with a supply conductor 5 in order to apply' potentials. Then an insulating layer 3' is applied again and subsequently again a grid l provided with a supply conductor 6. Thus one proceeds until the required number of grids is pres- .ent and lastly an insulating vlayer is applied to What we claim is: v

1. An electrode system for the detection or ampliilcation of electric currents comprising a pair of main electrodes in spaced relation, one of which has a high emitting capacity and is .made of a Vmetal from the group including silver,

copper and aluminum, and the other of which l has a low emitting capacity and is made from selenium, a plurality of control electrodes also in spaced relation interposed between the main electrodes, and thinr layers of insulating material.

interposed between and contacting with the sur'l lfaces of adjacent control electrodes and the surfaces vof adjacent main and control electrodes.

` 2. An electrode system as defined in claim l, wherein an artificial resin constitutes the layers of insulating material between the several electrodes.

3. An electrode system as defined in claim 1 wherein the control electrodes are made from aluminum, the surfaces of which have been oxidized.

GILLES HOLST.l

WIILEM CHRISTIAAN VAN GEEL. 25 

